Radiation-Induced Changes in Tumor Vessels and Microenvironment Contribute to Therapeutic Resistance in Glioblastoma

This study aimed to investigate the effect of radiation on tumor growth and the GSC microenvironment in a mouse model of glioma. To evaluate the growth-inhibitory effects of ionizing radiation on GSCs, tumor volume was measured via anatomical magnetic resonance imaging (MRI) after the intracranial injection of 1 × 104 human patient-derived GSCs (83NS cells), which exhibit marked radioresistance. When a tumor mass of ~5 mm3 was detected in each animal, 10 Gy of cranial irradiation was administered. Tumor progression was observed in the orthotopic xenografted GSC tumor (primary tumor) from a detectable tumor mass (5 mm3) to a lethal tumor mass (78 mm3) in ~7 d in the non-irradiated group. In the RT group, tumor growth was halted for almost 2 weeks after administering 10 Gy cranial irradiation, with tumor growth resuming thereafter and eventually approaching a lethal mass (56 mm3) 21 d after radiation. Radiation therapy yielded good therapeutic effects, with a 2-fold increase in GSC glioma survival; however, tumor relapse after RT resulted in higher mortality for the mice with a smaller tumor volume (p = 0.029) than the non-irradiated tumor-bearing mice. Moreover, tumor regrowth after IR resulted in different phenotypes associated with glioma aggressiveness compared with the non-irradiated mice; the apparent diffusion coefficient by diffusion MRI decreased significantly (p < 0.05, 0 Gy vs. 10 Gy) alongside decreased angiogenesis, abnormal vascular dilatation, and upregulated...
Source: Frontiers in Oncology - Category: Cancer & Oncology Source Type: research